This invention relates to a cast resin having superior mechanical strength and optical properties such as transparency and refractive index.
Recently, the resin glass which is superior to inorganic glass in impact-resistance, lightweight, castability and dyeability has become popular in the field of eye-glass lenses. The resin glass may be exemplified by polymethyl methacrylate, polydiethylene glycol bis-allyl carbonate, polystyrene or polycarbonate. However, the above-mentioned polymethyl methacrylate or polydiethylene glycol bis-allyl carbonate, while being superior in lightweight, impact-resistance and castability, suffers from the drawback that they are not suited to high magnification and reduction in weight because their refractive index is as low as about 1.49 and a larger lens thickness than in the case of the inorganic glass is required if they are to be used as lenses. On the other hand, the above-mentioned polystyrene or polycarbonate, while having a high refractive index of the order of 1.58 to 1.59, suffers from the drawback that since they are thermoplastic resins, they are susceptible to optical distortion due to double refraction during injection molding, while being inferior in resistance to solvents or scratch-resistance and being low in Abbe's number or adhesivity to a hard coat film which is deposited for improving surface hardness. Various technological proposals have been made for overcoming the above-mentioned deficiencies. For example, a resin glass consisting of a copolymer of diethylene glycol bis-allyl carbonate and diallyl isophthalate has been proposed in Japanese Laid-Open Patent Publication No.53-7787 (1978), while a resin glass consisting of a copolymer of diallyl isophthalate and di(meth)acrylate having Bisphenol A and diethylene glycol bis-allyl carbonate has been proposed in Japanese Laid-Open Patent Publication No.59-191708 (1984). However, these resin glasses suffer from the drawback that they are poor in impact-resistance and weatherability and that a non-reacted monomer tends to be left due to the difference in copolymerizabilty to render it difficult to control the reaction during the polymerization process.
Besides, a resin glass consisting of a dibenzyl fumarate-diallyl phthalate copolymer has been proposed in Japanese Laid-Open Patent Publication No.62-235901 (1987), while a resin glass consisting in a copolymer of dibenzyl itaconate or dibenzyl mesaconate with diallyl phthalate and a resin glass consisting of a copolymer of diallyl tere(iso)phthalate prepolymer, methyl (meth)acrylate and an aromatic mono(di) carboxylic acid (alkyl)allylester have been proposed in Japanese Laid-Open Patent Publication No.64-45412 (1989) and in Japanese Patent Publication No.1-60494 (1989). However, these resin glasses suffer from a drawback that they are inferior in impact-resistance.
A resin glass consisting of a diethylene glycol bis-allyl carbonate oligomer proposed in Japanese Laid-Open Patent Publication No.59-140214 (1984) has a drawback that it is low in refractive index and may become stained in color.
A resin glass consisting of a diallyl terephthalate oligomer-vinyl monomer copolymer proposed in Japanese Laid-Open Patent publication No.3-54213 (1991), has a drawback that it is inferior in impact-resistance.
A resin glass consisting of a copolymer of a styrene derivative with a heavy metal salt of unsaturated carboxylic acid, and a resin glass consisting of a copolymer of a nucleus halogen-substituted diallyl phthalate with a nucleus halogen-substituted allyl benzoate, proposed in Japanese Laid-Open Patent Publications Nos.57-28115 (1982) and 60-55007 (1985), respectively, suffer from the drawback that while having a higher refractive index of the order of 1.58 to 1.60, they are higher in specific gravity and hence inferior in lightweight because of the content of larger amounts of heavy metal ions and halogen atoms.
A resin glass consisting of a copolymer of a styrene monomer and a di(meth)acrylate monomer containing Bisphenol A with an aryl methacrylate monomer has also been proposed in Japanese Laid-Open Patent Publication No.55-13747 (1980). This resin glass has, however, a drawback that the lens formed of the resin glass tends to be stained in color, while the resin glass is inferior in impact-resistance and adhesivity to a hard coat film.
A resin glass consisting of a copolymer of a hydroxy di(meth)acrylate having an aromatic ring, a diisocyanate monomer and a styrene monomer has been proposed in Japanese Laid-Open Patent Publication No.59-133211 (1984). This resin glass has a drawback that while having a higher refractive index of the order of 1.60, it is only poor in weatherability and higher in specific gravity. Finally, a resin glass which is prepared by mixing a peroxyester as a curing agent to a monomer composition composed of methacrylate, a polyfunctional methacrylate and diacrylate and curing the resulting mixture by heating and which is superior in transparency and high in refractive index, has been proposed in Japanese Laid-Open Patent Publication No.3-70715 (1991). This polymer has, however, a drawback that it is inferior in adhesivity to a hard coat film and has a higher specific gravity.